Actually, Lee, I'd suggest checking with BC Ferries. Always good to go to the source.

At last news, the ferry itself was aground and no-one knows how long it will be there, and with what damage. Because there were divers still in the water, other routes' ferries were being kept out of the bay. Even when the area is cleared and the other ferries are again able to use the terminal, having one non-functioning ferry means there'll be lineups even longer than usual for a long summer weekend . . . at ALL terminals. People go where they think they'll have a better chance of getting on-board, whether Horseshoe Bay or Tsawwassen.

Having a reservation is a good idea, though. An extra $15 is sometimes well worth it.